[FIXED] Embedded Jersey 3 with Jetty into existing Application

Issue

i am trying to embed a HTTP-Server into an existing java Application. My goal is to create a small rest API as an interface to send commands to the server application it runs in.

I planned using Jakarta and Jersey 3 with Jetty as embeded HTTP-Server. My starting point was the following topic which was for Jersey 2 but i tried my luck: Embed jersey in java application

My problem is that i get 404 Not Found back when i try to call http://localhost/login/status in my browser. The page is blank. When i switch to using Grizzly2 as embedded HTTP-Server and type the url in the browser, the result is the same. The only difference in Grizzly2 i could spot is when i only call http://localhost/ i get an error page additionally to the 404 Not Found response back. As soon as i add /login to the url, i get the 404 Not Found response without an error page. What could be the reason the server does not pick up my resources?

I am using the Eclipse IDE. First i created a clean Maven project, added the following dependencies and created my test code:

org.glassfish.jersey.core -> jersey-server
org.glassfish.jersey.containers -> jersey-container-jetty-http

On my first startup i got some missing class errors, searched for the dependencies they are in and added them to the pom. Following is my current test code.

<!-- pom.xml -->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>test-ee</groupId>
    <artifactId>test-ee-embed</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.glassfish.jersey</groupId>
                <artifactId>jersey-bom</artifactId>
                <version>3.0.4</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.glassfish.jaxb</groupId>
                <artifactId>jaxb-bom</artifactId>
                <version>3.0.2</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>jakarta.servlet</groupId>
            <artifactId>jakarta.servlet-api</artifactId>
            <version>5.0.0</version>
        </dependency>
        <dependency>
            <groupId>jakarta.xml.bind</groupId>
            <artifactId>jakarta.xml.bind-api</artifactId>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.core</groupId>
            <artifactId>jersey-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.inject</groupId>
            <artifactId>jersey-hk2</artifactId>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jaxb</groupId>
            <artifactId>jaxb-runtime</artifactId>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-servlet</artifactId>
        </dependency>
        <dependency>
            <groupId>org.glassfish.jersey.containers</groupId>
            <artifactId>jersey-container-jetty-http</artifactId>
        </dependency>
    </dependencies>
</project>

// LoginserverRestApi.java
package de.l2d;

import org.glassfish.jersey.server.ResourceConfig;

import jakarta.ws.rs.ApplicationPath;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;

@ApplicationPath("/login")
public class LoginserverRestApi extends ResourceConfig {

    @GET @Path("/status")
    public String status() {
        // TODO Return real server statistics.
        return "{\"status\":\"ok\"}";
    }

}

// RestApiServer.java
package de.l2d;

import java.net.URI;

import org.eclipse.jetty.server.Server;
import org.glassfish.jersey.jetty.JettyHttpContainerFactory;

import jakarta.ws.rs.core.UriBuilder;

public class RestApiServer {
    private Server server;

    private RestApiServer() {
        URI baseUri = UriBuilder.fromUri("http://localhost/").build();
        server = JettyHttpContainerFactory.createServer(baseUri, new LoginserverRestApi(), false);
    }
    
    public void start() throws Exception {
        server.start();
    }
    
    public void stop() throws Exception {
        server.stop();
    }

    private static final class SingletonHolder {
        protected static RestApiServer instance = new RestApiServer();
    }
    public static RestApiServer getInstance() {
        return SingletonHolder.instance;
    }
}

// Main.java
package de.l2d;

public class Main {
    public static void main(String[] args) throws Exception {
        RestApiServer.getInstance().start();
        Thread.currentThread().join();
        RestApiServer.getInstance().stop();
    }
}

Solution

I found the solution to my problem. However, i do not know why it behaves like this.

I had to use the Path annotation instead of the ApplicationPath annotation on the LoginserverRestApi class and additionally construct a ResourceConfig with LoginserverRestApi.class as parameter and pass that Object to the JettyHttpContainerFactory.createServer static method. Following are the two files which differ from the initial post:

// LoginserverRestApi.java
package de.l2d;

import org.glassfish.jersey.server.ResourceConfig;

import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;

@Path("/login")
public class LoginserverRestApi extends ResourceConfig {

    @GET @Path("/status")
    public String status() {
        // TODO Return real server statistics.
        return "{\"status\":\"ok\"}";
    }

}

// RestApiServer.java
package de.l2d;

import java.net.URI;

import org.eclipse.jetty.server.Server;
import org.glassfish.jersey.jetty.JettyHttpContainerFactory;
import org.glassfish.jersey.server.ResourceConfig;

import jakarta.ws.rs.core.UriBuilder;

public class RestApiServer {
    private Server server;

    private RestApiServer() {
        URI baseUri = UriBuilder.fromUri("http://localhost/").build();
        ResourceConfig config = new ResourceConfig(LoginserverRestApi.class);
        server = JettyHttpContainerFactory.createServer(baseUri, config, false);
    }
    
    public void start() throws Exception {
        server.start();
    }
    
    public void stop() throws Exception {
        server.stop();
    }

    private static final class SingletonHolder {
        protected static RestApiServer instance = new RestApiServer();
    }
    public static RestApiServer getInstance() {
        return SingletonHolder.instance;
    }
}

Answered By - Christian
Answer Checked By - Candace Johnson (JavaFixing Volunteer)